Hydraulic jet drilling method using ferrous abrasives



Den 1968 R, J. sooowm ETAL 3,416,514

vHYDRAULIC JET DRILLING METHOD USING FERROUS ABRASIVES 2 Sheets-Sheet 1Filed Dec. 27, 1965 QJ. Q

INVENTORSI ROBERTJ. GOODW I ERNEST A. MORI, JOSEPH L. PE/(AREK, 1241/4 WSCI/.405 ROBERT'E. Z/NKHAM v1958 R. J. GOODWIN ETAL 3,416,614

HYDRAULIC JET DRILLING METHOD USING FERROUS ABRASIVES 2 Sheets-Sheet 2Filed Dec. 27, 1965 (53/13/W) in? do Hie/3C7 mvswroRs' ROBERT J. aaaoww,ERNEST .A. MORI,

JOSEPH L. PE/(APE'K, PAUL W 567/408 9 ROBERT 1 Z/IV/(IMM United StatesPatent HYDRAULIC JET DRILLING METHOD USING FERROUS ABRASIV ES Robert J.Goodwin, Oakmont, Ernest A. Mori, Hampton Township, Allegheny County,and Joseph L. Pekarek and Paul W. Schaub, Penn Hills Township, AlleghenyCounty, Pa., and Robert E. Zinkham, Richmond, Va., assignors to GulfResearch & Development Company, Pittsburgh, Pa., a corporation ofDelaware Filed Dec. 27, 1965, Ser. No. 516,290 4 Claims. (Cl. 175--67)ABSTRACT OF THE DISCLOSURE A method of drilling hard rock formations inwhich particles of ferrous abrasives having a size in the range of 7 to80 mesh are suspended in a drilling liquid. The drilling liquid ispumped down rotating drill pipe in a well and discharged at a velocityof at least 500 feet per second through tungsten carbide noZZles in adrill bit at the lower end of the drill pipe to cut the formation beingdrilled. The ferrous abrasives give increased drilling rates withreduced wear of the nozzles in the drill bit.

This application is a continuation-in-part of copending application Ser.No. 311,088, entitled Method and Apparatus, fi'ed Sept. 24, 1963 byRobert J. Goodwin, Ernest A. Mori, Joseph L. Pekarek, Paul W. Schaub andRobert E. Zinkham, now abandoned.

This invention relates to the drilling of wells, and more particularlyto an improved drilling process in which a stream of drilling liquidcontaining suspended ferrous abrasive is discharged at extremely highvelocities against the bottom of a borehole to drill through hardformations.

Improvements in conventional rotary drilling processes have greatlyincreased rates of drilling in soft formations and formations of mediumhardness. To a large extent, the improvements have resulted from morepowerful equipment which allows the application of greater bit weightsto cone or drag-type bits. One type of bit that is used widely to drillsoft formations is referred to as the jet bit. It differs from the usualbit principally in directing the drilling mud against the bottom of thehole to clean the bottom of the hole rather than over the surface of thecutters to keep the cutters clean. The purpose of jet bits is to improvethe removal of cuttings broken from the formation by the mechanicalcutting elements of bits rather than to cut grooves in the formationbeing drilled; however, some penetration of soft formations by thestream of drilling mud may be responsible for some of the increase indrilling rate. Quick removal of the cuttings from the bottom of the holereduces shielding of the bottom of the ho e from the bit by the cuttingsand reduces regrindin-g of cuttings. The conventional jet bits have beenineffective in increasing substantially the rate of drilling in hardformations.

Recently, a novel hydraulic jet drilling process which is effective inincreasing the rate of drilling of hard formations has been developed.In the hydraulic jet drilling process, an abrasive-laden liquid isdischarged at extremey high velocities against the bottom of the hole tocut the formation being drilled and remove cuttings from the hole.Substantially all of the penetration of the rock being drilled in thehydraulic jet drilling process is accomplished by the abrasive-ladenstream, and mechanical removal of rock from the bottom of the hole byengagement with a bit is restricted to removal of ridges which mayextend upward between grooves cut by the high-velocity stream. In thehydraulic jet drilling process, the weight applied to the nozzle head,referred to for convenience as the bit, is approximately one-fourth, orless, of the weight applied in comparable conventional drilling methods.Hydrau ic jet drilling in hard formations is substantially faster thandrilling with conventional rock bits but is still relatively slowcompared to drilling in soft formations, and further increases inhydraulic jet drilling rates are desirable.

The high velocity at which the abrasive-laden stream passes throughnozzles in the bit causes rapid erosion of the nozzle with a resultantincrease in the diameter of the orifice in the nozzle. Because the rateof drilling is highly dependent upon the velocity at which theabrasive-laden stream strikes the bottom of the borehole, the reducedvelocity resulting from enlargement of the nozzle orifice reduces thedrilling rate and makes it necessary to replace the bit. In deep wells,a substantial part of the rig time can be used in making the round tripsnecessary to replace the bit. For this reason, it is important to reducethe rate of erosion of the nozzles.

When the high-velocity stream of abrasive-laden liquid strikes theformation being drilled, the abrasive, aswell as the formation, issubjected to severe stresses. When sand is used as the abrasive in thedrilling, approximately one-half of the sand is broken up in a singlepass through the bit into fine particles unsuited for further use. Thelarge amounts of abrasive consumed cause the abrasive to be an importantpart of the cost of the hydraulic jet drilling process. It is desirableto use an abrasive that breaks up only to a negligible extent onstriking the bottom of the borehole and, hence, can "be reused to reducethe abrasive requirements.

This invention resides in a hydraulic jet drilling method for thedrilling of boreholes in hard formations in which a ferrous abrasive issuspended in a liquid to form a drilling liquid that is dischargedthrough nozzles spaced at different distances from the center ofrotation of a drill bit to cut a plurality of concentric grooves overthe major portion of the bottom of the borehole. The drilling liquid isdischarged from the nozzles at a distance of inch to 1% inches above thehighest portion of the bottom of the borehole and at a velocity of atleast 500 feet per second. The liquid in which the ferrous abrasive issuspended to form the drilling liquid has an apparent viscosity on theFann viscometer of at least 50 centipoises at 600 rpm. and a minimumzero gel strength, also measured on the Fann machine, of 50 pounds persquare feet both before and after passing through the nozzles.

FIGURE 1 of the drawings is a diagrammatic flow sheet of this inventionshowing a system for handling the drilling liquid used in the drillingprocess of this invention with the lower portion of the boreholeenlarged.

FIGURE 2 is a chart comparing the rate of penetration of a hard rock bya drilling liquid containing a ferrous abrasive with the rate ofpenetration by a drilling liquid containing sand in hydraulic jetdrilling processes.

FIGURE 3 is an enlarged diagrammatic view of the drill bit shown inFIGURE 1.

In the hydraulic jet drilling process of this invention, particles offerrous abrasive are suspended in a liquid to form a drilling liquidwhich is pumped down drill pipe having a drill bit mounted on its lowerend. The drill bit has a plurality of nozzles opening through its lowerend for discharging the drilling liquid at a high velocity against thebottom of the borehole to penetrate the bottom of the borehole. Thenozzles are positioned at different distances from the center ofrotation to cut a plurality of concentric grooves in the bottom of theborehole as the bit is rotated. The nozzles may be positioned to cutoverlapping grooves, but it is preferred that the nozzles be positionedto cut a central hole in the bottom of the borehole and a plurality ofconcentric grooves spaced from one another to leave intervening ridgeswhich can easily be mechanically broken.

The drilling liquid is pumped down the drill pipe at a rate and pressureto cause a pressure drop through the orifices of at least about 4,000p.s.i. to impart a velocity of at least 500 feet per second, andpreferably more than 600 feet per second, to the drilling liquiddischarged from the nozzles. Stand-off bars on the bottom of the drillbit body extend downwardly below the nozzle outlets and maintain thedesired spacing of inch to 1 /4 inches from the nozzle outlets to theridges on the bottom of the borehole.

After the discharge from the nozzles, the drilling liquid and entrainedcuttings circulate upwardly through the borehole around the drill pipeand are discharged at the surface for treatment to remove cuttings andput the drilling liquid in condition for recirculating in the drillingsystem.

The ferrous abrasive used in the hydraulic jet drilling process of thisinvention may be either cast iron particles or steel particles readilyavailable as commercial products used in the cleaning and treating ofmetal surfaces. Ferrous abrasives can be manufactured by blowing ahighvelocity stream of air or steam against molten cast iron or steel toseparate globules of the metal. The globules are blown into water wherethey are chilled. The solidified particles are heat treated and gradedby size. Grit is prepared by crushing shot and then heat treating thegranular particles and grading them according to size. Either angulargranular particles, referred to as grit, or rounded particles, referredto as shot can be used, but the shot are preferred because of fastercutting rates obtained with them.

The ferrous particles used in this invention have a size larger than 80mesh in the US. Sieve series. The drilling rate is faster with theparticles of larger size, and it is desirable to use the largestparticles that will pass through the nozzles in the drill bit withoutplugging the nozzles and that can be handled by the high-pressure pumps.In nozzles having an orifice Ms inch in diameter, ferrous abrasiveparticles in the range of 7 to 80 mesh can be used. A preferred range ofabrasive particle sizes is 16 to 50 mesh. Larger particles can be usedwith larger orifices, but it is not possible to handle particles muchlarger than 7 mesh with the pumps presently available. An arrangementthat has been used successfully with inch nozzles is to screen allcuttings and abrasive particles larger than mesh before delivering themto the high-pressure pumps. Ferrous abrasive particles in the 50-80 meshrange cause drilling rates approximately equal to sand particles in thepreferred range of particle sizes for sand and are retained in thedrilling liquid to reduce the amount of abrasives required.

The ferrous abrasive particles are suspended in a drilling liquid in aconcentration of /2 to 6 percent, preferably 1 to 4 percent by volume.Higher concentrations increase the amount of abrasive in the system andthe total break-up of the abrasive without a corresponding increase indrilling rate. Lower concentrations of abrasive markedly reduce thedrilling rate.

Drilling liquids suitable for use in hydraulic jet drilling processesusing sand as an abrasive are not suitable for use in this invention.The drilling liquids used to suspend the ferrous abrasive must have arelatively high gel strength and viscosity to remove the abrasive fromthe hole during the drilling operation and to prevent settling of theabrasive in the borehole when it is necessary to stop the circulation ofthe drilling liquid. The drilling liquid should have a minimum viscosityof at least 50 centipoises as determined on the Fann viscometer at 600rpm. and an initial or zero time gel strength of at least 50 pounds per100 square feet. The drilling liquid should have a pH of at least 8.5and preferably in the range of 8.5-10. Viscosities and gel-strengthsabove the minimum specified are necessary to prevent excessive settlingof the ferrous abrasive from the drilling liquid on those occasions whencirculation of the drilling liquid in the hole is interrupted. We havefound that many of the compositions ordinarily employed to increase theviscosity of liquids suffer a serious reduction in viscosity uponpassing at high velocities through nozzles such as those in the drillbit. It is not only essential that the drilling liquid have the minimumspecified viscosity in gel strength as it is pumped down the drill pipe,but it is also essential that the viscosity and gel strength of thedrilling liquid be above the minimums specified after passing throughthe nozzles at a rate resulting in a pressure drop through the nozzlesof at least 4,000 p.s.i.

A suitable drilling liquid is an invert emulsion of water and diesel oilcontaining 30 to 60 percent oil, with the oil in the continuous phase. Apreferred drilling liquid is an invert emulsion containing 40 to 50percent diesel oil. The emulsion can be stabilized by, for example, asulfurized potassium soap of tall oil containing 5 percent sulfur. Otheremulsifiers, such as polyhydric alcohol fatty acid esters, sulfatedsperm oil soaps, and polyvalent metal soaps of rosin acids can be used.The pH of the drilling liquid is adjusted to the range of 9 to 10 by theaddition of alkaline material such as caustic soda. Another suitabledrilling liquid is an aqueous dispersion of bentonite containing 2percent bentonite and l .to 2 percent Flosal, a fibrous asbestosmaterial. The Flosal drilling mud should have a pH of 8.5 to 9.5 toreduce corrosion of the drilling equipment and abrasive. Hydraulic jetdrilling with a ferrous-abrasive-laden drilling liquid is not limited tothe use of any particular drilling liquid as long as the drilling liquidhas adequate gel strength and viscosity to give satisfactory suspensionof the abrasive particles.

For purposes of illustration, a hydraulic jet drilling process will bedescribed in which 20 to 40 mesh particles of lndogrit, a cast irongranular material, manufactured by Industeel Company of Pittsburgh, Pa.,is suspended in a concentration, by volume, of 2 percent in an invertemulsion drilling liquid containing 50 percent dieseloil. The drillingliquid is delivered by high-pressure pumps 10 through a line 12 into thedrill string 14 of a drilling rig 16 suitably equipped to rotate thedrill string in the borehole. The drilling liquid is pumped at a highrate downwardly through the drill pipe 14 and discharged against thebottom 18 of the borehole 20 through nozzles /s inch in diameter in abit 22 at the lower end of the-drill pipe. Drill pipe 14 is rotated at arate of at least 5 rpm. during the drilling.

The drilling liquid and entrained cuttings pass upwardly through theborehole and are discharged therefrom through line 24 and delivered to ashale shaker 26 in which oversize cuttings larger than 10 mesh areremoved from the drilling liquid. Ferrous-grit-laden drilling liquid isdelivered through line 28 to a bank of cyclone separators 30 in whichabrasive particles are separated from the liquid and delivered as anunderflow through line 32. Overflow from separators 30 is deliveredthrough line 34 to a second bank 36 of separators in which furtherclean-up of ferrous-grit particles from the drilling liquid isaccomplished, and the ferrous-grit particles separated in separators 36are discharged as underfiow through line 38.

Overflow from separators 36, which contains less than 0.2 percentparticles larger than 200 mesh, is delivered into a storage tank 40.Ferrous-grit-free drilling liquid is withdrawn from tank 40 through line42 and passed through another bank of cyclone separators 44 for removalof fine solid particles of 200 mesh size and smaller to reduce theconcentration of larger than 200 mesh particles to a trace and controlthe density of the drilling liquid. Clean drilling liquid from theseparators 44 is delivered through line 46 to the high-pressure pumps10. Abrasive from lines 32 and 38 is mixed with the clean drillingliquid for recirculation in the well. Because of the low rate of break-up of ferrous abrasives, removal of fines from all of the liquidcirculated in the borehole is not required and drilling liquid may bedelivered from the shale shaker directly to pumps 10 through a suitablyvalved bypass line 48. Heat exchangers 47 and 49 are provided forcontrol of the tance of A inch to 1% inches above the ridges in thebottom of the borehole. Stand-off bars 62 are also subjected to severeabrasion and are constructed of a hard material such as tungstencarbide. By cutting a central hole and a temperature of the drillingliquid- A e p r ture f 4 5 plurality of closely spaced concentricgrooves, the inter- 170 F. is preferred when using the invert emulsiondrillvening ridges are thin and unsupported which allow them ing mud.Tests on nozzles in the drilling bit have indicated t b readily b k f oth b tt f th h l by th that drilling liquid temperatures above 140 F.increase t d- 1f b nozzle life- Valves at e provided as required toallow The ferrous grit particles are effective in increasing the liveryof liquid from tank 40 directly or indirectly through drilling rate overthat which is obtained with other abrasepafatofs t0 P p 10, Or tocirculate the drilling sive particles such as sand. A series of testswas made in q Ah Screen 51 in line 12 eIhOVeS large Solid which theabrasive-laden drilling liquid was discharged Particles which might PhOZZleS in the drill Make'up from a single nozzle onto a block of hardblack granite abrasive is added to the system at shale shaker 26 fromrotated in a horizontal plane about an i 11 inches Storage pp 15 fromthe bit axis at a rate of about 30 r.p.m. The outlet of For effectivedrilling by the hydraulic l drilling the nozzle was maintained /2 inchfrom the original rock method, the drilling llquid must be discharged ata Veloe' surface during the tests. The tests were made at a nozzle ltyof at least 500 feet P Second, and Preferably at least inlet pressure of5,000 p.s.i. and a drilling liquid velocity 600 per second: from nozzleshaving an Outlet 1/2 of approximately 776 feet per second. Each test wasconto 11/2 m f bottom the borehole- In tintued for a period of 20seconds after which the depth of cal hydrauhc let drlnmg opfiranon thefour Pumps 10 the out was measured to give an indication of the drillingsupPly a total of about 21000 t 2,400 PQ i rate. Test runs were made ondrilling liquids containing deliver 450 to 600 gallons per mlnute of thedrilllng l quid difierent Concentrations of 20 40 mesh cast iron and ata pressure of 5,000 p.s.1. to the drill pipe 14 for delivery with Sandof the same Size The results are Presented in a drill bit havingPluriility typical S FIGURE 2. The data presented in FIGURE 2 ShOW that1 g. sutch an Operatlon W111 have 10 to 20 nozzles Inch ferrousabrasives cause much higher drilling rates than sand in hydraulicdrilling operations.

Refemng FIGURE blt 22 1S Shqwn havlpg During the cutting test describedabove, the drilling liq- Outer nozzles 52 54 posltloned and slanting touid samples were caught, diluted, screened, dried, weighed, charge?stream agamst the .bottom of the borehole and sieved, and reweighed.These data were then reduced to locimon to cut a hole having d enoughgauge to an average percentage of particles larger than 40 mesh gf f i ia g zggsg ggi fi fi g' gz sggg broken to smaller than 40 mesh. Theresults of the partoward the center of rotation of the drill bit to cuta central tlcle breakup determmauons are presented m Table hole in thebottom of the borehole. Intermediate nozzles TA I 58 are providedbetween the inner nozzle 56 and the outer Matarial and mesh rangfi.Percent breakup nozzles to cut grooves in the bottom of the borehole be-20 40 mesh Sand 50 60 tween those out by the inner nozzle and the outernozzle. 204) mesh Steel i fig The number of intermediate nozzles 58 andtheir location 20 40 mesh ferrous grit 14 will depend upon the size ofthe borehole being cut. A sufiicient number of nozzles at differentradial distances Because Of the eXtfeIhelY g VelOCltleS 0f the dfllhhgfrom the center of rotation of the drill bit should be proliq p gthrough the nozzles, erosion f the nozzles vided to cause penetration ofthe formation being drilled is n important factor in determining thefeasibility of to be accomplished by the high velocity abra iv t amdra=ulic jet drilling. A series of tests was run in which 20 and tocause the major portion of the rock removal to be to 40 mesh sandparticles were pumped through a nozzle the result of cutting by theabrasive stream. The nozzles having a inch diameter inlet tapering downto a /8 inch may be positioned so that there is some overlapping of thediameter orifice over a distance of 2 /2 inches and a paths traveled bythe drilling liquid discharged from the straight section A; inch longand A5 inch in diameter exnozzles. It is preferred, however, that thenozzles be tending from the orifice to the nozzle outlet. In the test,spaced to cut grooves in the bottom of the borehole sepa- 5O suspensionsof 20 to 40 mesh cast iron and of 20 to 40 rated by thin, easily brokenridges that are exposed on mesh sand were caused to flow through thenozzle at rates their inner and outer faces whereby they can be easilygiving a pressure drop across the nozzle of 5,000 p.s.i. or broken bybit weights not exceeding about 700 pounds more. The nozzles wereconstructed of two types of tungper inch diameter. sten carbide. Theresults of the tests are presented in The nozzles in the bottom of thebit for the discharge Table II.

TABLE II.NOZZLE WEAR TESTS [Test duration, 6 hours] Pressure Increase inNozzle designation Abrasive Cone. per- (p.s.i.) nozzle cent by Vol.across diameter nozzle (inch) Tungsten carbide I Cast iron 1. 5 7, 0000.0018

D Sand (20-40)- 6 5, 000 0. 004-0. 005 Tungsten Carbide II Cast iron 1.5 7, 000 0. 0036 Sand (20-40) 6 5, 000 0. 013

support the bit with the orifice outlet at the desired dis- The resultspresented in Table II show that nozzle wear is much lower when a ferrousabrasive is suspended in the drilling liquid than when the abrasive issand in spite of the fact that the ferrous abrasive causes a much higherdrilling rate. Because the drilling rate is a measure of the ability ofthe drilling liquid to out a hard surface, it is surprising that thenozzle erosion is less when iron grit is suspended in the drillingliquid than when sand is suspended in the drilling liquid.

Both cast iron and steel shot and grit are highly advantageous inhydraulic jet drilling operations in making possible high drilling ratesthrough very hard rock formations. The high drilling rates can beobtained with a relatively low rate of erosion of the nozzles throughwhich the drilling liquid is discharged against the bottom of the hole.Moreover, the low rate of breakup of the ferrous grit particles allowstheir repeated use, and thereby greatly reduces the cost of the abrasiverequired in hydraulic jet drilling.

We claim:

1. A hydraulic jet drilling process for the drilling of boreholes inhard rock formations comprising suspending 7-80 mesh ferrous abrasiveparticles in a concentration of /2 to 6 percent by volume in a liquid toform a drilling liquid having a minimum viscosity of 50 centipoises at600 rpm. on the Fann viscometer, a zero gel strength of at least 50pounds per 100 square feet, and a pH of at least 8.5, pumping thedrilling liquid down drill pipe in the borehole to a bit mounted on thelower end of the drill pipe, discharging the drilling liquid fromdownwardly opening nozzles in the bit at a velocity of at least 500 feetper second, rotating the bit whereby the streams of drilling liquiddischarged from the nozzles cut a plurality of concentric grooves in thebottom of the borehole, said nozzles being spaced at different radialdistances from the center of the bit whereby a central hole and aplurality of concentric grooves are cut in the bottom of the boreholewith the outer groove having desired borehole diameter and the groovesare separated by intervening ridges having a maximum thickness of about/2 inch, supporting the drill bit on said intervening ridges with theoutlet of the nozzles A1 inch to 1 1 inches above the ridges, andcirculating cuttings upwardly around the drill pipe.

2. A process as set forth in claim 1 in which the pressure drop throughthe nozzles is at least 4,000 p.s.i.

3. A hydraulic jet drilling process as set forth in claim 1 in which thedrilling liquid is an invert emulsion and is passed through heatexchangers before pumping down drill pipe in the borehole to maintainthe drilling liquid in 8 the range of to F., and the internal surfacesof the nozzles are tungsten carbide.

4. A hydraulic jet drilling process for the drilling of boreholes inhard rock formations comprising suspending 7-80 mesh ferrous abrasiveparticles in a concentration of /2 to 6 percent by volume in a liquid toform a drilling liquid, delivering the drilling liquid down drill pipein a well to a drll bit, rotating the drill bit about a vertical axis,discharging the drilling liquid at a velocity of at least 500 feet persecond downwardly and outwardly from outwardly slanting first nozzles inthe bit near the perimeter thereof to cut a borehole of the desiredgauge, discharging drilling liquid downwardly and inwardly at a velocityof at least 500 feet per second from an inwardly slanting nozzlepositioned near the center of the bit to cut a central hole, dischargingdrilling liquid downwardly at a velocity of at least 500 feet per secondfrom intervening nozzles between the first nozzles and the inwardlyslanting nozzle to cut grooves in the bottom of the borehole withintervening ridges having a maximum thickness of about /2 inch,supporting the bit on the bottom of the borehole with the nozzle outletsinch to 1% inches above the bottom of the borehole, circulating thedrilling liquid and entrained cuttings upward through the boreholearound the drill pipe, and discharging the drilling liquid and entrainedcuttings from the well at the ground surface.

References Cited UNITED STATES PATENTS 878,208 2/1908 Kirschniok 672,315,496 4/1943 Boynton 166222 X 2,758,653 8/1956 Desbrow 166222 X3,130,786 4/1964 Brown 166-223 X FOREIGN PATENTS 230,078 7/ 1925 GreatBritain.

JAMES A. LEPPINK, Primary Examiner.

